Replacing GXP chainset on a TriCross

Discussion in 'Cycling Equipment' started by resentin, Mar 26, 2013.

  1. resentin

    resentin New Member

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    Hi everyone,

    I'm totally new to the forum, and quite a novice bicycle user/modder too so please be patient should I ask silly questions :)

    I have just bought a second-hand Specialized TriCross Comp - model year 2010 (Shimano 105, double/10 speed). I could see that the chainrings were quite worn, but when serviced I was advised to replace BB (slightly worn) and chain as well (in worse state). I'd like to learn as much as possible about bike maintenance and be able to decide by myself what components adopt, even for the future, so I'll need some help and advice from the forums :) Thanks in advance to anyone who'll take the time to read and answer!

    Now, the stock chainset/BB was a Truvativ Elita GXP 48/34 (BB shell width 68mm), though the chainrings were replaced with a 50/36 set.

    I'd like to ask dozens of specific questions but the short version is:
    What would you suggest?

    More specifically:
    • shall I keep the same BB standard (GXP) or change?
    • Is it possible, say, put a GXP BB and a non-GXP crankset?
    • When you replace the chainrings, do you automatically get a whole new chainset (so with cranks)?
    • I see 46/38, 46/36, 50/34 and other options (funny enough, no 48/34) in online shops. Pro/Cons of these options (beyond the obvious difference in how they affect speed)?
    • I can't seem to find - in online shops and for a given chainset - different options for the shell width. Does it mean they would all fit? Need adapters?
    • Can I use any 10speed chain with any chainring I'll choose?
    • I was advised to look at KMC chain / cassette (yes I might replace that too!). Would they do with any choice I'll make for the other components?

    If there's any specific product you'd advise, please attach the link to the shop selling it!

    Note: I mainly use the bike for commuting in London (15 miles/day - often in the rain) but I do plan to do some medium-range touring on it as well. Also I may do some triathlon in the future, for the fun of it rather than with competitive hopes though. I'm obviously not a power cyclist and I'm rather on a budget but usually not lean towards the cheapest option anyway.

    Many many thanks and sorry for the lengthy post!

    R
     
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  2. alfeng

    alfeng Well-Known Member

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    If your bike has visibly external BB cups AND the frame's BB shell's width is 68mm, then the bike has an ENGLISH THREADED (1.37X24) BB shell ... and, you will have the greatest number of current-or-future options with regard to Crankset & BB choice

    • external BB cups often have the threading informaton silk screened on the outer circumference of the cups
    • the driveside of the an English threaded BB cup is LEFT HANDED
    • both Italian cups have RIGHT HAND threads (36x24)

    If you do not see external BB cups, then look for a decal on the front of the downtube near the BB, and it will tell you the type of BB which your frame has ...

    AFAIK, there are adapters for frames designed to use BB30 & BB86 [plus, M.O.st & Ashtabula/"American"] BBs which allow you to use an English threaded BB.

    You do NOT have to change both Chainrings at the same time, BTW ... change the one you want, as needed.

    I recommend that you choose-and-use Shimano chains regardless of the crankset ...

    • do NOT remove the cosmolene from a Shimano chain ...
    • do NOT use one of the many "chain cleaners" which attach to the chainstay regardless of the chain ...
    • I recommend AGAINST using an ultrasonic cleaner for cleaning your chain unless you are a Track (velodrome) racer
    • DO oil your chain, regularly ... 3-in-1 oil (or, equivalent weight "household"-type oil) works for me ... many people have a favorite chain lube, BUT why pay more?

    You can simply replace the bearings, BTW ...

    Both FSA MegaExo & Shimano Hollowtech II bearings actually have a 24mm Inner Diameter, but the plastic sleeve makes the effective Inner Diameter 25mm ... so, almost any set of replacement bearings with a 25mm ID & the proper outer diameter intended to replace a set of Hollowtech II or MegaExo bearings can probably replace your GPX's current BB bearings ...

    • unless things have changed, and they could have, the GXP BB spindle uses a 25mm ID bearing on the driveside & a 24mm ID bearing on the non-driveside, but the actual bearings probably have the same kluge to achieve the smaller inner diameter which Shimano & FSA use ...
    • heck, if you find a "spare" plastic bearing sleeve from an FSA or Shimano external BB then you can probably convert your GXP BB into a Shimano/FSA compatible BB, and vice-versa ...
    • if you are daring and/or handy, you can re-grease cartridge bearings ...

    Regardless you only need to change the actual crankset if you want to change the crank arm length OR if the cosmetics bother you [for example, you want a Campagnolo crankset OR if you want to pony up for a new 4-arm Dura Crankset!] OR you have a hankering for a Carbon Fiber crankset OR ____(?)____ ...
     
  3. resentin

    resentin New Member

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    Thank you Alfeng,

    lots of useful information there

    For the moment I won't venture into fixing and greasing but that's something I'll start doing at some point!
     
  4. alfeng

    alfeng Well-Known Member

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    Errata.

    BTW. Thanks for being able to read past the typo. The correct statement should, of course, read:
    Both FSA MegaExo & Shimano Hollowtech II bearings actually have a 25mm Inner Diameter, but the plastic sleeve makes the effective Inner Diameter 24mm ...
     
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